Clock Frequency

Question 1

The floating point unit of a processor using a design D takes 2t cycles compared to t cycles taken by the fixed point unit. There are two more design suggestions D1 and D2. D1 uses 30% more cycles for fixed point unit but 30% less cycles for floating point unit as compared to design D. D2 uses 40% less cycles for fixed point unit but 10% more cycles for floating point unit as compared to design D. For a given program which has 80% fixed point operations and 20% floating point operations, which of the following ordering reflects the relative performances of three designs? (Di > Dj denotes that Di is faster than Dj)

A
D1 > D > D2
B
D2 > D > D1
C
D > D2 > D1
D
D > D1 > D2
       Computer Organization        Clock Frequency       Gate 2007-IT
Question 1 Explanation: 
T = 0.8 × time taken in fixed point + 0.2 × time taken in floating point
D = 0.8 × t + 0.2 × 2t = 1.2t
D1 = 0.8 × 1.3t + 0.2 × 0.7 × 2t = 1.32t
D2 = 0.8 × 0.6t + 0.2 × 1.1 × 2t = 0.92t
⇒ D2 > D > D1
There is 1 question to complete.